Method of preparing secondary battery

Patent metadata

Field	Value
Publication number	US-2018191024-A1
Application number	US-201715740920-A
Country	US
Kind code	A1
Filing date	Mar 30, 2017
Priority date	Mar 31, 2016
Publication date	Jul 5, 2018
Grant date	—

Abstract

The present invention relates to a method of preparing a secondary battery which includes providing a film layer, which includes a first solvent having a melting temperature of 25° C. or more and a viscosity of 1.5 cP or more, between a separator and an electrode (step 1), preparing an electrode assembly by using the electrode, the film layer, and the separator (step 2), and accommodating the electrode assembly in a case, injecting an injection solution including a second solvent, and sealing the case (step 3), and a secondary battery prepared by the method. According to the method of preparing a secondary battery of the preset invention, since electrolyte solution impregnability may be improved, performance and safety of the secondary battery may be further improved.

First claim

1 . A method of preparing a secondary battery, the method comprising steps of:
providing a film layer, which includes a first solvent having a melting temperature of 25° C. or more and a viscosity at 40° C. of 1.5 cP or more, between a separator and an electrode (step 1); preparing an electrode assembly by using the electrode, the film layer, and the separator (step 2); and accommodating the electrode assembly in a case, injecting an injection solution including a second solvent, and sealing the case (step 3).

2 . The method of claim 1 , wherein the providing of the film layer (step 1) comprises steps of:
(a) after preparing a film layer in a freestanding form by compressing the first solvent in a solid state at a temperature of less than 25° C., providing the film layer between the separator and the electrode, or (b) after melting the first solvent in a solid state at a temperature of less than 25° C., providing the film layer by directly coating one side or both sides of the separator with the first solvent.

3 . The method of claim 1 , wherein the first solvent comprises at least one compound selected from the group consisting of ethylene carbonate, cis-4,5-dimethyl-1,3-dioxolan-2-one, trans-4,5-dimethyl-1,3-dioxolan-2-one, 1,2-cyclopentylene carbonate, cyclohexene carbonate, pinacolone cyclic carbonate, 1,3-propylene carbonate, 5,5-dimethyl-1,3-dioxan-2-one, sulfolane, ethyl methyl sulfone, diethyl sulfone, ethyl dimethylcarbamate, and phenyl dimethylcarbamate.

4 . The method of claim 1 , wherein the film layer further comprises a softener.

5 . The method of claim 4 , wherein the softener comprises a single material selected from the group consisting of a polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, an ethylene-propylene-diene monomer (EPDM), a sulfonated EPDM, a styrene-butadiene rubber (SBR), and a fluorine rubber, or a mixture of two or more thereof.

6 . The method of claim 4 , wherein a weight ratio of the first solvent to the softener in the film layer is in a range of 99.5:0.5 to 90:10.

7 . The method of claim 1 , wherein the film layer has a thickness of 10 μm to 500 μm.

8 . The method of claim 1 , wherein the film layer further comprises a first lithium salt.

9 . The method of claim 8 , wherein the first lithium salt is included in a concentration of 0.3 M to 2.0 M with respect to the first solvent.

10 . The method of claim 1 , wherein the second solvent comprises at least one selected from the group consisting of a low-viscosity solvent, which is a liquid at room temperature and has a viscosity at 25° C. of less than 1.5 cP, and a high-viscosity solvent which is a solid at room temperature and has a viscosity at 40° C. of 1.5 cP or more.

11 . The method of claim 10 , wherein, in a case in which the second solvent is the low-viscosity solvent,
the second solvent comprises a single material selected from the group consisting of carbonates; esters; and lactones, or a mixture of two or more thereof.

12 . The method of claim 11 , wherein the second solvent comprises a single material selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, butylene carbonate, diethyl carbonate, dipropyl carbonate, fluoroethylene carbonate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, and γ-butyrolactone, or a mixture of two or more thereof.

13 . The method of claim 10 , wherein, in a case in which the second solvent is a high-viscosity solvent,
the second solvent comprises a single material selected from the group consisting of ethylene carbonate, cis-4,5-dimethyl-1,3-dioxolan-2-one, trans-4,5-dimethyl-1,3-dioxolan-2-one, 1,2-cyclopentylene carbonate, cyclohexene carbonate, pinacolone cyclic carbonate, 1,3-propylene carbonate, 5,5-dimethyl-1,3-dioxan-2-one, sulfolane, ethyl methyl sulfone, diethyl sulfone, ethyl dimethylcarbamate, and phenyl dimethylcarbamate, or a mixture of two or more thereof.

14 . The method of claim 1 , wherein the injection solution further comprises a second lithium salt.

15 . The method of claim 14 , wherein the second lithium salt is included in a concentration of 0.7 M to 3.0 M with respect to the second solvent.

16 . The method of claim 1 , wherein a weight ratio of the first solvent to the second solvent is in a range of 1:0.2 to 1:2.

17 . A secondary battery prepared by the method of claim 1 , the secondary battery comprising:
a positive electrode, a negative electrode, a separator, an electrolyte solution, and a film layer, which includes a first solvent having a melting temperature of 25° C. or more and a viscosity at 40° C. of 1.5 cP or more, disposed in at least one position between the separator and the negative electrode or between the separator and the positive electrode.

18 . The secondary battery of claim 17 , wherein the electrolyte solution comprises a second solvent and a second lithium salt.

19 . The secondary battery of claim 17 , wherein the film layer further comprises a first lithium salt, and
the electrolyte solution comprises a second solvent and a second lithium salt.

20 . The secondary battery of claim 17 , wherein the film layer further comprises a first lithium salt, and
the electrolyte solution is composed of a second solvent.

Assignees

• Lg Chemical Ltd

Inventors

• Yu Sung Hoon

Classifications

• H01M10/058 Primary

  Construction or manufacture · CPC title

• H01M4/64

  Carriers or collectors · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M2004/027

  Negative electrodes · CPC title

• H01M4/525

  of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy · CPC title